During the operation of a washing machine, particularly during spin cycles, the machine can sometimes experience an extreme vibration. These vibrations can even cause displacement of the washing machine as it “walks” across a surface such as a floor. Typically, this event is due to the different shapes and densities of the clothing or objects that are being washed which, after the washing cycle and the draining of the wash basket, can stick together and cause differences in the center of mass inside the wash basket. The vibration problem can also be caused by the introduction of relatively heavier objects into the washing basket such as e.g., shoes.
By way of example, after the wash cycle and the draining of the wash fluid from the basket, the shoes may be located on one side of the wash basket or positioned in a manner that causes the center of mass of the rotating system to be off center. As the wash basket is rotated, particularly at high speeds during e.g., a spin cycle, the off centering and centrifugal forces create an imbalance that can generate undesired strain in the washing machine components, an undesirable level of noise, and/or “walking” of the appliance. In an extreme or prolonged situation, the imbalance created by the excessive vibration can also wear-out and damage the washing machine components.
As a result, in order to prevent this imbalance, various devices have been proposed. For example, washing machines have been equipped with balance rings, which are typically hollow rings that rotate with the wash basket. Inside the ring (or toroid) a weight such a liquid or solid balls have been inserted. During operation, the ring will act as a counterweight to the imbalance because the liquid or solid balls will move to a position within the ring that counters the centrifugal forces created by the articles in the wash and thereby balance the basket during rotation. Balance rings of various configurations including chambers, partitions, and other elements to improve the balancing effect have also been proposed.
For washing machines, the above mentioned balance rings are typically attached or connected in some manner with the wash basket or other rotating component. For example, for a vertical axis washing machine, the balance ring can be attached to the top and/or bottom of the wash basket chamber. For a horizontal axis washing machine, it can be attached to the front, back, or both ends of the washing chamber.
With balance rings that incorporate counterweights within the balance ring, it is important that such weights move freely within the annular spaces of balance ring so as to readily provide a counter balance during spinning of the wash basket. If the counterweights become stuck at a certain position in the balance ring or cannot move freely, then the balance ring will not be able to counter an imbalance in the wash basket.
Balance rings can be constructed from a variety of materials including plastics. Using e.g., injection molding, one or more parts can be created from plastic materials and then combined to create the balance ring. Certain challenges exist with using plastic to create the balance ring. For example, in the molding of the plastic parts of the balance ring, the plastic is injected in a molten state into the mold and then allowed to cool. As the plastic cools, it typically solidifies from the outside of the mold surface towards the inside of the mold. In thicker sections of the plastic part, this can result in stresses that pull inwardly on the part as the plastic contracts so as to create depressions—sometimes referred to as sink marks—on the surfaces of the plastic part. For a balance ring, such sink marks can be formed on one or more surfaces that form the annular space inside the ring through which the counterweights must move during rotation of the wash basket. These sink marks can undesirably impede the movement of the counterweight as discussed above.
Accordingly, a balance ring for balancing the load of a rotating element within an appliance, such as e.g., the wash basket of a washing machine, would be beneficial. More particularly, a balance ring constructed so as to eliminate or minimize sink marks so that one or more counterweights within the ring can move freely would be useful.